Mediator

Mediator: a hub that coordinates peers

Problem: many objects need to talk to each other. Wire them directly and you get an N-to-N tangle where everyone references everyone.

PawWalk scenario: a dispatch center. Walker, owner, and tracker don't hold references to each other — they notify the mediator, which routes to the others.

The mediator centralizes the 'who tells whom' logic so the peers stay decoupled.